Anybody here good at Physics?

Discussion in 'Random Topic Center' started by Gir, Sep 6, 2007.

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  1. Gir

    Gir New Member

    I'm having trouble in this class and I need some help on my homework. I don't want answers, just how to set up the problems and stuff.
  2. Magic_Umbreon

    Magic_Umbreon Researching Tower Scientist, Retired

  3. PSYCO829

    PSYCO829 New Member

    i can help, depending on what you need to know
  4. Gir

    Gir New Member

    Velocity and force.

    An airplane flying toward 0 degrees at 100 km/h is being blown toward 90 degrees at 40 km/h. What is the resultant velocity of the plane?

    Three people are pulling on a tree. The first person pulls with 15 N at 65 degrees; the second with 16 N at 135 degrees; the third with 11 N at 195 degrees. What is the magnitude and direction of the resultant force on the tree?

    I keep getting confused on how to set them up.

    Back to back posts merged. The following information has been added:

    For the force problem I got 27.04 N, NW at negative 54.85 degrees.

    For the velocity problem I got 107.7 km/h at 21.8 degrees. At least I tried.
    Last edited: Sep 6, 2007
  5. doctormcdreamy

    doctormcdreamy New Member

    just find the formulas and plug and chug. that's not so hard.
  6. Gir

    Gir New Member

    What are the formulas?
  7. Sandslash7

    Sandslash7 <a href="

    First you use the formula (using the degrees and force for the first direction) giving you some number, than get a different number using the degrees and force of the second direction. Then get the average and use the formula to find the degrees and force for the new direction.

    Sorry if that's a bit unhelpful, but its been over a year and a half since I went over the material.
  8. Articjedi

    Articjedi Active Member

    All of these force vectors can be translated in terms of an x and a y force. It's been a couple years, but with the angles and each force you get a set of right triangles to work with. I'd like to draw a pic but the gym won't let me for obvious reasons. If you turn each force into a vector then add up each of the x and y directions you get a resultant force in a specific direction.
  9. Mew*

    Mew* Active Member

    Solution: Beg your friends for answers in the morning on the bus.......Just kidding. :)

    Just tell your teacher that the dog ate your homework, they'll always understand.

    I have no idea how to do this stuff :lol:
  10. doctormcdreamy

    doctormcdreamy New Member

    yeah. just come in early for school and ask your teacher for help. that's what i always do. back when i was taking it.
  11. Gir

    Gir New Member

    Did anyone try to answer it? I think I did it right but I have nothing to compare my answers to. I called my friend, but he didn't know how to do it either.
  12. Sandslash7

    Sandslash7 <a href="

    I'd try to, but I don't have my Physics book with me. (plus, it kind of helps you learn the material if YOU do it. That's how I learned, with many MANY problems)
  13. Azure Kite

    Azure Kite New Member

    You could always try wikipedia or or something....or not. Anyway I wouldn't recomend lying about it or gettin your friends to tell you but it would be a good idea to talk to your teacher before or after school one day or even ask your parents about it. If you really need help you could get a tutor or something but only if absolutely necesessary. I wouldn't personally know it because, well, I'm not that smart when it comes to physics.
  14. Zapditto

    Zapditto New Member

    That site should be of a lot of help. I would do the problems to check your answers but I don't have pen/paper with me. I haven't taken a physics class in ages. But remember - always draw a picture! And every equation you will ever use in physics can be derrived from F = ma. So really you only need to "memorize" one equation and you can derrive really anything from there. Some of the derrivations are difficult but knowing that you can derrive it from there really helps in many situations.
  15. doctormcdreamy

    doctormcdreamy New Member

    amen brother.
  16. Azure Kite

    Azure Kite New Member

    I think you ment "amen brotha".
  17. Jim Ferrell

    Jim Ferrell New Member

    I thought I'd help you out by saying that your answer on the velocity problem is completely correct. I'm pretty sure your other answer is correct as well.

    But as others have said, these sort of things take a lot of practice. And remember, when summing up vectors, add them up tip to tail. It helps out immensely when setting up these sort of problems.

  18. Gir

    Gir New Member

    Sandslash - I DID do the problems. I'm looking to see if what I did was correct. Since I can't contact my teacher and my friends don't know, I figured I would see if I could get any help here. Obviously you didn't learn the material if you need your book to solve the problems.

    Thank you all for your help.
  19. Sandslash7

    Sandslash7 <a href="

    IC, IC.

    Well, I must have missed that part. Oh, well. You did a good job on them, and got a pretty resonable answer.
  20. ixidor89

    ixidor89 New Member

    For number one:

    Velocity = ((100km/h)^2 + (40km/h)^2)^1/2 = 108km/h
    Direction = arctan(40km/h/100km/h) = 21.8 degrees
    You would probably want to convert the velocity to mks, so hours to seconds and kilometers to meters:

    108km/h * 1h/3600s * 1000m/1km = 30m/s

    For number two:

    Y = 15Nsin(65) + 16Nsin(135) + 11Nsin(195) = 22N
    X = 15Ncos(65) + 16Ncos(135) + 11cos(195) = -16N
    Total = ((22N)^2 + (-16N)^2)^(1/2) = 27N

    Direction = arctan(22/-16) = -54 degrees.

    Yup, it looks like you did everything right. Judging by the numbers shown in the problem, you might want to check your significant figures, though.

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